Earth
Overview
Our planet earth is the third planet from the Sun, and it is the largest of the four inner planets that are made of rocks and metallic substances. The name earth comes from an English/German word which means ‘the ground’.
Planet earth seems to be the only planet that (we know of) supports life in the solar system. Liquid water covers 66% of its surface. Hospitable temperature, vast oceans, and the availability of required chemical ingredients enabled the beginning of life 3.8 billion years ago. Despite the incredible scientific advancements, the origin of life on Earth still remains a mystery.
However, one thing is evident. The rarest of all the rare incidents that happened in the solar system (and possibly in the Universe) is the emergence of life on Earth. A chain of most improbable coincidences had led to the beginning and the subsequent gradual evolution of life. Ultimately, it culminated in the development of intelligent life on our planet.
It is apparent that our planet’s environment is unique, and that life, which took billions of years to evolve, is extremely precious. So, it is everyone’s responsibility to protect Earth’s unique environment and to help nature sustain life on Earth.
If you are curious about whether humans are alone in the universe, check out this post: Are We Alone in The Universe.
Earth's Moon
Earth possesses a single natural satellite, the Moon. The gravitational effects of the Moon are responsible for oceanic tides and play a significant role in stabilizing the axial tilt of the planet. This stabilized tilt contributes to long-term consistency in Earth’s climate and seasonal cycles on a cosmic timescale. Many people believe that the presence of the Moon may have been instrumental in enabling life to develop on Earth.
Moon’s Origin: While the two terrestrial planets Mercury and Venus do not have any moon orbiting them, Mars has two miniscule objects which are really captured asteroids. How did it happen that our Earth has such a massive Moon? What is the origin of our Moon? Astronomers believe that out Moon formed because a Mars-sized object collided with Earth when it was young.
Have you ever thought about why only one side of the Moon is visible from Earth? If you’re interested in learning more about why we always see the Moon’s near side, please read this post: why does the Moon always show the same side to earth?
Interesting Facts
Atmosphere: Earth’s atmosphere consists of nitrogen (78%), oxygen (21%), and other gases (1%) including carbon dioxide. The atmosphere, along with Earth’s strong magnetic field, acts as a shield to protect life from all the elements of cosmos.
Size: It has a radius of 6371 kilometers, and it is the largest of the four inner planets closest to the Sun.
Orbit: The orbit of Earth around the Sun is almost circular with a mean distance of about 150 million kilometers from the Sun. The average distance between Earth and the Sun is known as an Astronomical Unit (AU). Astronomers sometimes use AU to specify the distance between celestial objects.
Earth takes 365.25 days to orbit the Sun, and its tilt is 23.4 degrees from the plane of its orbit. This tilt is responsible for the yearly cycle of seasons.
References:
- The Cambridge Guide to the Solar System by Kenneth R. Lang, Cambridge University Press.
- https://solarsystem.nasa.gov/planets/earth/in-depth/